Eleonora, Pierre, Aritomi, Yuhang

Recently we found 50 Hz presents everywhere. In the attached figures, we can see some examples of these 50Hz noises.

A part of noise level was identified that it comes from of ground loop between circuit and measurement device. This is identified by changing the power supply of the oscilloscope to different places. But we cannot eliminate this noise totally. (From figure 5 to figure 2, the change is the change of oscilloscope power supply)

We also identified that the 50Hz noise for GRMC transmission signal comes from the DDS board. At that moment, only DDS board output is connected to mixer and mixer IF channel is connected to the oscilloscope. We tried to change the connection with and without a lot of other components, and we found only DDS board gives this 50Hz noise.  (Figure 3)

We see a different shape with normal measurement 50Hz noise for GRMC transmission signal, so we think this noise coupled into control loop and affects the phase locking of GRMC a lot. (Figure 2)